System for detaching an occlusive device within a mammalian body using a solderless, electrolytically severable joint

ABSTRACT

A solderless sacrificial link between a detachable member which is placed at and is intended to remain at a desired site within the mammalian body and the core wire used to introduce the detachable member. The detachable member device may be one used to create emboli in the vascular system or may be of any other type deliverable into the human body and detached into an ionic aqueous environment, either for later removal or permanent placement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.08/743,494, filed Nov. 4, 1996, now U.S. Pat. No. 6,123,714, which is acontinuation of U.S. patent application Ser. No. 08/485,502, filed Jun.7, 1995, now abandoned, which in turn is a divisional of U.S. patentapplication Ser. No. 08/367,061, filed Dec. 30, 1994, now abandoned, theentirety of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention is an apparatus primarily used for endovascular occlusionthrough the formation of thrombi in arteries, veins, aneurysms, vascularmalformations, and arteriovenous fistulas. In particular, it deals witha solderless sacrificial link between a detachable device which isintroduced to and is intended to remain at the desired site within thebody and the core wire used to introduce the detachable device. Thedetachable device may be one used to create emboli in the vascularsystem or may be of any other type deliverable into the human body anddetached into an ionic aqueous environment, either for later removal orpermanent placement.

BACKGROUND OF THE INVENTION

Approximately 25,000 intracranial aneurysms rupture each year in NorthAmerica. The primary purpose of treatment for a ruptured intracranialaneurysm is to prevent rebleeding. There are a variety of ways to treatruptured and non-ruptured aneurysms. Possibly the most widely known ofthese procedures is an extravascular approach using surgery ormicrosurgery. This treatment is common with intracranial berryaneurysms. The method comprises a step of clipping the neck of theaneurysm, performing a suture ligation of the neck, or wrapping theentire aneurysm. Each of these procedures is formed by intrusiveinvasion into the body and performed from the outside of the aneurysm ortarget site. General anesthesia, craniotomy, brain retraction, andplacement of a clip around the neck of the aneurysm are typicallyrequired in these surgical procedures. The surgical procedure is oftendelayed while waiting for the patient to stabilize medically. For thisreason, many patients die from the underlying disease or defect prior tothe initiation of the procedure.

Another procedure—the extra-intravascular approach—involves surgicallyexposing or stereotactically reaching an aneurysm with a probe. The wallof the aneurysm is then perforated from the outside and varioustechniques are used to occlude the interior in order to prevent it fromrebleeding. The techniques used to occlude the aneurysm includeelectrothrombosis, adhesive embolization, hog hair embolization, andferromagnetic thrombosis. These procedures are discussed in U.S. Pat.No. 5,122,136 to Guglielmi et al., the entirety of which is incorporatedby notice.

A still further approach is the least invasive and is additionallydescribed in Guglielmi et al. It is the endovascular approach. In thisapproach, the interior of the aneurysm is entered by use of a cathetersuch as those shown in Engelson (Catheter Guidewire), U.S. Pat. No.4,884,579 and also in Engelson (Catheter for Guidewire Tracking), U.S.Pat. No. 4,739,768. These patents describe devices utilizing guidewiresand catheters which allow access to the aneurysm from remote portions ofthe body. Specifically by the use of catheters having very flexibledistal regions and guidewires which are steerable to the region of theaneurysm, embolic devices which may be delivered through the catheterare an alternative to the extravascular and extra-intravascularapproaches.

The endovascular approach typically includes two major steps. The firststep involves the introduction of the catheter to the aneurysm siteusing devices such as shown in the Engelson patents. The second stepoften involves filling the aneurysm in some fashion or another. Forinstance, a balloon may be introduced into the aneurysm from the distalportion of the catheter where it is inflated, detached, and left toocclude the aneurysm. In this way, the parent artery is preserved.Balloons are becoming less in favor because of the difficulty inintroducing the balloon into the aneurysm sac, the possibility of ananeurysm rupture due to overinflation of the balloon within theaneurysm, and the risk associated with the traction produced whendetaching the balloon.

A highly desirable embolism-forming device which may be introduced intoan aneurysm using endovascular placement procedures, is found in U.S.Pat. No. 4,994,069, to Ritchart et al. There is described adevice—typically a platinum/tungsten alloy coil having a very smalldiameter—which may be introduced into an aneurysm through a cathetersuch as those described in Engelson above. These coils are often made ofwire having a diameter of 2-6 mils. The coil diameter may be 10-30 mils.These soft, flexible coils may be of any length desirable andappropriate for the site to be occluded. For instance, the coils may beused to fill a berry aneurysm. Within a short period of time after thefilling of the aneurysm with the embolic device, a thrombus forms in theaneurysm and is shortly thereafter complemented with a collagenousmaterial which significantly lessens the potential for aneurysm rupture.Coils such as seen in Ritchart et al. may be delivered to thevasculature site in a variety of ways including, e.g., mechanicallydetaching them from the delivery device as is shown in U.S. Pat. No.5,250,071, to Palermo or by electrolytic detachment as is shown inGuglielmi et al. (U.S. Pat. No. 5,122,136) as was discussed above.

Guglielmi et al. shows an embolism-forming device and procedure forusing that device. Specifically, Guglielmi et al. fills a vascularcavity such as an aneurysm with an embolic device such as a platinumcoil which coil has been endovascularly delivered. The coil is thensevered from its insertion tool by the application of a small electriccurrent. Desirably, the insertion device involves a guidewire which isattached at its distal end to an embolic device by an electrolytic,sacrificial joint. Guglielmi et al. suggests that when the embolicdevice is a platinum coil, the platinum coil may be 1-50 cm. or longeras is necessary. Proximal of the embolic coil is a guidewire, oftenstainless steel in construction. The guidewire is used to push theplatinum embolic coil, obviously with great gentleness, into thevascular site to be occluded. The patent shows a variety ways of linkingthe embolic coil to the pusher guidewire. For instance, the guidewire istapered at its distal end and the distal tip of the guidewire issoldered into the proximal end of the embolic coil. Additionally, astainless steel coil is wrapped coaxially about the distal taperedportion of the guidewire to provide column strength to the guidewire.This coaxial stainless steel wire is joined both to the guidewire and tothe embolic coil. Insulation may be used to cover a portion of thestrength-providing stainless steel coil. This arrangement provides fortwo regions which must be electrolytically severed before the emboliccoil is severed from the guidewire.

A further variation of the Guglielmi Detachable Coil is one in which thedistal tip of the stainless steel guidewire is not soldered to theproximal end of the embolic device. A simple conical stainless steelwire is included from the stainless steel guidewire to the embolic coil.

A further variation found in Guglielmi et al. includes a thin,threadlike extension between the guidewire core and the proximal end ofthe embolic coil. In this way, the guidewire does not extend to theembolic coil, but instead relies upon a separately introduced extension.

A continuation-in-part of the Guglielmi et al patent discussed abovefiled on Feb. 24, 1992 entitled “[IMPROVEMENTS] IN AN ENDOVASCULARELECTROLYTICALLY DETACHABLE WIRE AND TIP FOR THE FORMATION OF THROMBUSIN ARTERIES, VEINS, ANEURYSMS, VASCULAR MALFORMATIONS AND ARTERIOVENOUSFISTULAS” now U.S. Pat. No. 5,354,295 issued Oct. 11, 1994 describes theuse of mechanically detachable embolic devices as well as those whichare electrolytically detachable. The embolic devices may be augmentedwith attached filaments.

Dr. Taki has devised a variation of the Guglielmi detachable coil usinga copper link between the guidewire and the coil.

None of the noted procedures using electrolytically detachable embolicdevices suggests the concept of eliminating the solder in thesacrificial link, specifically by crimping and welding the detachabledevice to the associated pusher. This permits clean detachment of theembolic device in a facile and quick fashion.

SUMMARY OF THE INVENTION

As noted above, this invention is a joint which is severable byelectrolysis in an aqueous environment within the human or mammal body.It may be used in combination with a member which is placed into thebody either via creation of an artificial opening, e.g., by introductioninto the vasculature, or by use of a normally existing opening, e.g., byplacement in the genito-urinary tract. The member so-placed may eitherremain in place or may be later removed. The preferred device is one incombination with an embolus-forming member for forming a vascularocclusion at a selected site. Generally, the preferred device comprisesa guidewire, or core wire, having a distal tip which distal tip may beintroduced into the selected vascular site or cavity. The core wire isjoined to the distal tip or embolic device in such a way that thevascular device may be electrolytically detached by application of acurrent to the core or guidewire. The improvement to the preferredvariation involves the use of a specifically formed, discrete,sacrificial link between the core wire and the vascular device to allowclean and quick detachment from the core wire. The focussed electrolysisfound at the sacrificial site provides a clean severed joint and apredictable time for electrolysis.

There are several variations of the sacrificial joint each, however,involving a solderless, usually crimped and welded, joint between thecore wire and the detachable member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-7 show sideview, partial cross-sectional views of variations ofthe inventive, electrolytically susceptible, sacrificial link between acore wire and an embolic device.

FIG. 8 shows side view of a typical assembly involving the inventivesacrificial link used in this invention.

FIGS. 9 and 10 schematically depict the method for deploying thevasoocclusive device using the inventive sacrificial link.

DESCRIPTION OF THE INVENTION

Each of the discrete sacrificial joints discussed below may be used inthe device shown in U.S. Pat. No. 5,122,136 to Guglielmi et al., theentirety of which patent is incorporated by reference.

It should be pointed out that one of the major benefits in using thesolderless joints specified in this application is the predictabilityfor time of detachment provided due to the absence of solder. Solder, itturns out, often provides a significant unknown in predicting the timefor detachment. Solders are not altogether uniform in theirconcentration once they have cooled and occasionally will create spotsof higher potential electrolytic activity because of a higherconcentration of a particular metal in the cooled solder flow.Additionally, the fluxes that must be used with such solders mayinadvertently be included as aberrations within the surface of thesolder and cause anomalies in the electrolytic degradation. Finally, thesolder itself will electrolytically degrade at a rate different thanthat of the sacrificial link. Elimination of the solder and use of asimpler cast of materials renders the predictability of electrolyticdetachment much more consistent.

FIG. 1 shows the details of the electrolytic joint 100. Specifically,shown in highly magnified cross-section is a detachable electrolyticdevice 102, in this case a coil. The detachable embolic device 102 is ofa material higher in the electromotive series than the material makingup the core wire 104 and, in particular, the area of the core wire 104which is to be dissolved (106). For instance, embolic coil 102 may be ofa material such as platinum or other noble metal, and the sacrificialarea 106 may be of steel, stainless steel, nickel, nickel/titaniumalloys, or other materials which will electrolytically dissolve in anaqueous fluid medium such as blood, saline solution, or other bodilyfluid prior to the dissolution of detachable device 102. The embolicdevice 102 in this stylized FIG. 1 is placed upon a sleeve 108 which isalso of a material more noble than is the material found in the corewire 104. The remainder of core wire 104 is covered in some fashion byan insulator 110. The length of the exposed electrolytic dissolutionarea 106 is quite short. For instance, it may be as short as 0.010inches, and typically is no longer than 0.150 inches in length.

The sleeve 108 need not be of the same material as is the detachabledevice or member 102. It simply requires that the sleeve 108 notdecompose prior to core wire 104. Suitable solder-less attachmentmethods for the sleeve 108 include crimping the sleeve onto the distalend of core wire 104, welding the sleeve 108 onto the core wire 104,screwing one into the other, or a combination of the steps. Obviously,other solderless methods will be apparent to the skilled worker afterreview of the disclosure herein. Further, the detachable device 102 isdesirably welded onto the outer surface of the sleeve 108 but may becrimped thereto.

The core wire 104 is covered with appropriate insulating material. Theseinsulating materials may be made of materials such aspolytetrafluoroethylene or other fluoropolymers (Teflon7), polyurethane,parylene, polyethylene, polypropylene, polyethylene terephthalate (PET),or other known suitable, typically polymeric, material. It is within thescope of this invention that the insulating material may equivalently bea coating of more noble metals, such as gold or the like. Thisequivalent layer may be plated or otherwise placed onto the core wire104. Again, it is the intent of this invention that the sacrificial area106 be narrowly outlined so that a small, discrete area of the core wireis exposed to the surrounding fluid for electrolytic dissolution. It isalso quite highly desirable that the area proposed for electrolyticdissolution be of a single dissolvable material completed clean of otherelectrolyzable materials. We have also found it desirable to coat theelectrolyzable area with one or more of the noted polymers, particularlyparylene, and remove a selected area by the use of an appropriately highenergy laser beam.

FIGS. 2-4 show variations of the distal portion of the core wire andmanner in which it can be made strong and protected from incidentaldissolution during electrolysis of the sacrificial joint 106 noted inthe discussion of FIG. 1 above.

FIG. 2 again depicts the combination 120 of the detachable embolicdevice 102, the distal end of core wire 104, and the noble metal sleeve108. More proximal to the dissolution area 106 is the assembly 122making up the distal portion of core wire 104. Here, core wire 104 isshown to have a taper prior to reaching a region of constant diameter.The core wire 104 is surrounded by distal core coil 124 and marker coil126. Distal coil 124 is placed for the purpose of providing columnstrength and flexibility to the distal section of the core wire assembly122 in the region near the dissolution area 106. Marker coil 126 isplaced to allow the attending physician, using a fluoroscope, to observewhether the core wire may be moved independently of the detachableembolic device assembly 120. If the core wire 104 is able toindependently move, then dissolution of the sacrificial leg is complete.In this variation, core wire assembly 122 utilizes a bushing 128 whichprotects core wire 104 from contact with surrounding bodily fluid. Thepolymeric bushing 128, in addition to providing insulation for the corewire 104, is shown to have a distal surface which is cut at an angle tothe axis of the core wire 104. This angle further delimits the area ofthe electrolytically sacrificial area 106 and additionally provides alever to help with separation of the joint once it is broken throughbecause of electrolysis. A castable polymer 130 is shown to be placed inthe region between the proximal end of marker coil 126 and about halfwaythrough the length of distal core coil 124. This cast or melted polymer,e.g., polyurethane, is used to secure the various coils in place withoutthe use of solder. Finally, an outer polymeric covering 132 is shown onthe outer periphery of distal core wire assembly 122. This outercovering 132 may be any of a variety of materials, but desirably is aslippery material such as a fluorocarbon, e.g., Teflon7. Other materialssuch as polyurethane or PET having a coating of a hydrophilic materialof the type described in the prior art is also useful. A tight sealbetween the polymeric bushing 128 and the outer covering 132 helpsassure that the core wire 104 sees a current only in the region desired.

FIG. 3 shows another variation of the joint depicted in FIG. 2, with theexception that a portion of coil 124 has been crimped and/or welded at aposition 134 near the distal end of the coil. Again, this crimp and/orwelding provides additional strength to the region of the core wireadjacent the polymeric bushing 128.

FIG. 4 depicts a further variation of the invention in which instead ofthe molten polymers described with regard to FIG. 2 or the crimping andwelding described in conjunction with FIG. 3, the core wire ismaintained in position using a glue or adhesive 136. These glues oradhesives may be any of a wide variety of known materials. For instance,they may be ultraviolet light curable polyacrylates or hot-meltadhesives or epoxies, to name just a few examples.

FIG. 5 shows a variation of the inventive joint using the glues oradhesives of (136) of FIG. 4 but depicting an insulator or more-noblemetallic plug (138) sealing the core wire 104 against intrusion ofsurrounding fluid. In this instance, the plug 138 has a face which isgenerally perpendicular to the axis of the core wire 104. The shape ofplug 138 is not particularly critical. A benefit has been noted for theslant cut plug or bushing shown in FIGS. 1, 2, 3 and 4, e.g., the slantcut provides a method for freeing the junction if difficulties with thejunction are encountered. Nevertheless, each shape works well.

As a further indication of the invention described herein, FIG. 6 showsa variation using somewhat different shapes for the opposing featuresfound on core wire 104 in which the area for electrolytic disintegrationis housed to help assure the absence of any open projection from theelectrolyzed joint. In this instance, however, a non-cylindricalattachment (140) has been attached to core wire. The depicted shape ofbushing 140 is spherical but it may just as well be olive shaped or plugshaped or any other convenient size or shape which is able to be crimpedand/or welded onto detachable embolic device 102. Similarly, oppositethe sacrificial zone 106 on core wire 104 may be found bushing 142.Again, bushing 142 may be of a shape convenient for the designer of thedevice. The composition of bushings 140 and 142 may be either of aninsulating material, e.g., a polymer, or of a metal more noble than thatfound in the bare core wire in the sacrificial region 106. In thisvariation, the sacrificial zone 106 is partially obscured by thepresence of extension 144. Extension 144 is allowed to remain for thespecific purpose of guarding the sacrificial zone 106 on the remotecircumstance that a core wire, once electrolyzed, does not cleanlydissolve. We have not found this to be the case in using bushings whichare welded and/or crimped to the core wire 104. It should be noted thatin FIG. 6, bushing 140 is crimped onto core wire 104 and detachablevasoocclusive device 102 is welded onto the distal side of bushing 140.

FIG. 7 shows a variation of the device shown in FIG. 6. Again, adetachable embolic device 102 is depicted. In this case, the detachableembolic device 102 is situated on the exterior surface of the bushing146. The bushing is crimped and welded to core wire 104. The detachableembolic device 102 is welded onto the exterior of bushing 146. The moreproximal portion of this device is similar to that shown, e.g., in FIGS.1, 2 and 5. Again, the absence of solder provides for a clearlydeterminable and controllable time period for detachment of thevasoocclusive device 102.

Vasoocclusive device 102 is shown in each of the drawings above to be acoil. It may be a coil or a braid or other vasoocclusive device as isalready known. The vasoocclusive device may be covered or connected withfibrous materials tied to the outside of the coil or braided onto theouter cover of the coil as desired. Such fibrous adjuvants may be foundin U.S. Pat. No. 5,382,259 to Phelps et al., or in U.S. Pat. No.5,226,911 to Chee et al., entitled “Vasoocclusion Coil with AttachedFibrous Elements”, the entirety of which are incorporated by reference.

Furthermore, the releasable member 102 need not be a vasoocclusivedevice or a device to create emboli. The member may be any membersuitable for detachment from the joint using electrolysis. These membersmay be, for instance, vena cava filters, vascular or bile duct stents,vaginally placed birth control devices, electrical activity monitoringleads, and any other device which my be either retained in place orlater removed.

FIG. 8 shows a typical layout involving the inventive discretesacrificial region 106 as was generally shown in the Figures above. InFIG. 8, a somewhat conventional Teflon7 laminated or similarly insulatedstainless steel core wire assembly 180 may be placed within a protectivecatheter. As was noted above, stainless steel core wire 180 may have adiameter of approximately 10-30 mils. In the noted embodiment in FIG. 8,core wire assembly 180 is tapered at its distal end to form a conicalsection 182 which joins a further section 184 which extends along alength of core wire 186. Section 184 then gradually narrows down to athinner section 188. The core wire assembly 180, as noted above, may beplaced within a catheter body and is typically 50-200 cm. in length downto sacrificial link 106. The distal section of core wire assembly 180has an outer Teflon7 sleeve 190 (or sleeve of other appropriateinsulating material). Furthermore, it has an end plug 192 to permitisolation of the guidewire electrically from the blood except atsacrificial discrete link 106. The proximal end of vasoocclusive device102 is typically a soldered tip or ajoint. Preferably, vasoocclusivedevice 102, when a coil, forms a secondary loop after it emanates fromthe end of the catheter. The distal end of vasoocclusive device 102 mayalso have an end plug or tip to prevent punctures of the aneurysm whenintroduced into the aneurysm sac.

As noted, the detachable member (e.g., a coil or vasoocclusive device)102 may be pre-biased to form a cylinder or conical envelope. However,the vasoocclusive device 102 is extremely soft and its overall shape iseasily deformed. When inserted within the catheter (not shown), thevasoocclusive device 102 is easily straightened so to lie axially withinthe catheter. Once ejected from the tip of the catheter, vasoocclusivedevice 102 may form a shape shown in FIG. 8 or may be loosely deformedto conform to the interior shape of the aneurysm.

FIG. 9 shows the placement of the inventive devices shown above within avessel 196 with the tip of catheter 198 placed near neck 200 of aneurysm202. Vasoocclusive device 204 is fed into aneurysm 202 at least untilsacrificial link 106 is exposed beyond the distal tip of the catheter198. A positive electric current of approximately 0.01-2 milli-amps at0.1-6 volts is applied to core wire 206 to form a thrombus withinaneurysm 202. The negative pole 208 of power supply 210 is typicallyplaced in electrical contact with the skin. It is also desirable thatthe current be allowed to return through a conductor placed in the wallof the catheter (or the guide catheter used in conjunction with thecatheter).

After the thrombus has been formed and the aneurysm occluded,vasoocclusive device 204 is detached from core wire 206 by electrolyticdisintegration of sacrificial link 106.

After sacrificial link 106 is completely dissolved by electrolyticaction, typically within 5 seconds to 5 minutes, the core wire 206 andcatheter 196, are removed from the vessel, leaving aneurysm 202 occluded212 as shown in FIG. 10.

The process is typically practiced under fluoroscopic control with localanesthesia. A transfemoral catheter is utilized to treat a cerebralaneurysm and is usually introduced at the groin. When the vasoocclusivedevice 204 is platinum, it is not affected by electrolysis. When thecore wire and pertinent portions of the supporting coils at the distaltip of the guidewire are adequately coated with insulating coverings,only the exposed portion at the sacrificial link 106 is affected by theelectrolysis.

Procedures for using this invention in non-vascular systems of the bodyare carried out in a similar fashion. The chosen site must be accessibleand the site must provide a local medium of sufficient ionic nature toallow electrolysis of the sacrificial joint to take place.

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of theinvention. Therefore, it must be understood that the shape of the distaltip or distal platinum coil used in combination with the core wireaccording to the invention may be provided with a variety of shapes andenvelopes.

EXAMPLE

Ten examples of the joint depicted in FIG. 3 were produced. The corewire was 0.003″ at the sacrificial joint, the joint was 0.005″ inlength. The distal bushing was a platinum alloy. Each of the exampleswas introduced into a saline solution and a voltage of 3.0 v at 1.0 mawas applied to the junction. The junction dissolved in a short period oftime—each between 44 seconds and 97 seconds.

The illustrated embodiments have been used only for the purposes ofclarity and should not be taken as limiting the invention as defined bythe following claims.

We claim as our invention:
 1. A mammalian implant assembly comprising: awire having an axis, a proximal end, and a distal end, a distal portionof the wire comprising a discrete metallic link that is susceptible toelectrolytic disintegration in an ionic medium, a section of the wireproximal of said link being insulated so as to not be susceptible toelectrolytic disintegration in the ionic medium; and a detachableimplant coupled to the wire by a solder-less attachment at a locationthat is distal to the discrete metallic link, the implant comprised of amaterial not susceptible to electrolytic disintegration in an ionicmedium.
 2. The assembly of claim 1 where the distal end of the wire hasa constant diameter.
 3. The assembly of claim 1 additionally comprisingmeans for providing column strength to the distal section of the wire.4. The assembly of claim 1, wherein the distal end of the wire istapered.
 5. A mammalian implant assembly, comprising: a wire having anaxis, a proximal end, and a distal end, a distal portion of the wirecomprising a discrete metallic link that is susceptible to electrolyticdisintegration in an ionic medium, a section of the wire proximal ofsaid link being insulated so as to not be susceptible to electrolyticdisintegration in the ionic medium; a detachable implant joined to thewire without solder, the implant comprised of a material not susceptibleto electrolytic disintegration in an ionic medium; and a sleevecomprised of a material not susceptible to electrolytic disintegrationin an ionic medium, the sleeve joining the wire to the implant.
 6. Theassembly of claim 5 where the sleeve is metallic.
 7. The assembly ofclaim 5, wherein the detachable implant is welded to the sleeve.
 8. Theassembly of claim 5, wherein the detachable implant is crimped onto thesleeve.